<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .container{
            font-size: 30px;
        }
    </style>
</head>
<body>
    <div class="container">
        abcdefgABCD
    </div>
    <script>
        // 1.把所有的字符串包裹一个span
        var containerEle = document.querySelector(".container");
        // trim()去掉首位空格；
        var str = containerEle.innerHTML.trim();
        var newStr = "";
        for(var i=0;i<str.length;i++){
            // console.log(str[i]);
            newStr += `<span>${str[i]}</span>`;
        }
        // console.log(newStr);
        containerEle.innerHTML = newStr;

        var spans = document.querySelectorAll(".container span");

        // 2.按对应的按键的时候改变 字符的颜色 
        document.onkeydown = function(e){
            var e = e || window.event;
            var key = e.key;
            spans.forEach(function(item){
                if(key==item.innerHTML){
                    item.style.color = "red";
                }
            })
        }

    //     var b = "badafd";
    //   var res =   b.charCodeAt(1);
    //   console.log(res);


    </script>
</body>
</html>